The high-pressure discharge lamps to which the present invention relates, and which are , for instance, shown in the referenced U.S. Pat. No. 4,647,814, Dobrusskin et al., assigned to the assignee of the present application, are particularly suitable for illumination of theater stages, television and motion picture film studios and the like. The light flux should be high and, further, have a color temperature which is similar to daylight, with a very good color rendition index. Such high-pressure discharge lamps have a discharge vessel, retaining a fill which includes metal halides. Prior art lamps of this type provide a light flux of over one million lumens; in a typical lamp, and with an operating current of 65 A and an arc power of 12 kW, a light flux of 1.1. mega lumens can be obtained. The electrodes within the discharge vessel are rod or pin-like and retained in the discharge vessel by being melt-sealed therein, with a molybdenum sealing foil providing a current supply connection for the electrodes.
The requirements for still higher light output and higher power lamps have led to investigations of loading of the current supply connection. To obtain still higher light flux, standard melt seals permit operating currents of at the most 100 A. Higher operating currents lead to excessive heating of the melt, and the molybdenum sealing foils tend to corrode, and separate from the seal. The metal halide fill in the lamp also causes devitrification of the discharge vessel, so that the average lifetime of the lamp is short and becomes economically unsatisfactory.
Other high-pressure discharge lamps of this type having a fill of mercury and a rare gas or of extra-high pressure rare gas are used specifically in the manufacture of electronic components.